Volt/VAR Optimization (VVO) is a utility-centric technology that focuses on the coordinated control of tap changers, voltage regulators, and shunt capacitors to achieve a global objective or objectives. The most common global objectives are the reduction of end-use energy and the regulation of power factor to a specified value. To achieve these goals, a general VVO system uses a combination of Conservation Voltage Reduction (CVR), which is achieved through the control of tap changers and voltage regulators, and power factor control, which is achieved through the control of shunt capacitors. When properly implemented, these systems will provide end-use customers with the same quality of service while reducing annual energy consumption. An increase in the efficiency of the system can also be achieved via reduced system losses, but it is a small effect compared to reductions at the end-use. The end result of a properly operated VVO system is lower energy usage and a more efficient system. Others systems may take a simpler approach of implementing CVR alone.
A VVO system has two main functional components. The first, and primary, function is the coordination of tap changers and voltage regulators, at the feeder level, to reduce energy consumption. The second function is the coordination of capacitors with a weighted dual objective of voltage flattening and power factor correction. In this system, the weighting of the voltage flattening is slightly higher than the weighting for power factor optimization.
One challenge that utilities face with VVO is verifying/validating the effectiveness of the system to their regulating authority. The validation of performance is generally achieved with a 60 or 90 day on/off evaluation process which requires the VVO system to be turned on or turned off on alternate days for the 60 or 90 day period, and is expensive and complicated. The 60 or 90 days evaluation period is required because of VVOs interaction with end-use loads that have thermal control loops, e.g. heating and cooling.
Generally outside firms are hired by utilities to conduct the evaluations, and execute the analysis. Commonly used VVO analysis protocol requires the VVO system to be turned on and off on alternate days for 90 days. Thus, during half of the evaluation process the system is off for testing purposes, representing a loss of benefits. The active power demand is adjusted to control for factors that affect the demand such as temperature, day of week, time of day, and on-days and off-days are compared to estimate the energy reduction achieved by the VVO system. Large amounts of data must be collected, and the analysis requires temperature correction of active power demand. As VVO deployments becomes more common and new installations require evaluation, the development of a simpler method, which requires a shorter period of data collection, to benchmark new evaluations would save time and money.